Graceful configuration reload
:::caution Next documentation
Diff-classified connection-pool reload was added after the 0.2.0 Private Preview. The 0.2.0 data plane does not provide the reload behavior described below.
:::
Not every connection-pool configuration change requires the same disruption. The runtime classifies a diff before applying it so safe changes can preserve live connections and structural changes can fail over deliberately.
Reload classes
| Class | Expected behavior |
|---|---|
| No-op | Effective configuration did not change. |
| Dynamic | Update runtime policy in place without touching established sockets. |
| Drain and reconcile | Close or replace idle capacity while allowing active work to complete. |
| Recreate required | Rebuild the affected runtime graph because the change cannot be applied safely in place. |
Unknown fields or an unrecognized diff must take the conservative recreate-required path.
Plan the change
- Review the configuration diff and predicted reload class.
- Check current client, server, idle, and in-flight connection counts.
- Confirm upstream connection capacity and retry behavior.
- Publish through the supported Manager workflow.
- Observe reload-class counters, idle drain activity, errors, and connection latency.
Ticker or maintenance-cadence changes can be dynamic when the installed release classifies them that way. Pool mode, authentication, endpoint, or other structural changes can require recreation.
Drain behavior
Drain applies to idle sockets first. It must not be treated as proof that all applications are interruption-free: clients can hold sessions, transactions, cursors, or long-running operations that affect termination timing.
Coordinate Kubernetes termination grace, readiness withdrawal, application retry, and MongoDB timeout settings.
Rollback
If errors or latency increase:
- Stop expanding the rollout.
- Restore the previous approved configuration revision.
- Confirm the resulting reload class.
- Verify client and upstream connection recovery.
- Preserve the diff and relevant metrics for investigation.
The exact field classification is release-specific. Check the installed bundle rather than assuming a newer or older release applies the same reload behavior.